The present invention relates to a lithography technique for manufacturing a semiconductor and, more particularly,-to an exposure method using a phase-shifting mask (PSM) and an exposure apparatus using the exposure method.
In a pattern formation method of transferring a pattern drawn on a mask to a wafer by using lithography, the pattern to be transferred must be fine and sharp. As one technique for meeting this demand, various phase-shifting masks are proposed. As a typical one, a Alternating phase-shifting mask formed by setting a phase difference of 180.degree. between two adjacent transparent portions is well known.
When, however, a mask (bright field mask) having a transparent peripheral portion in a main pattern is used as a Alternating phase-shifting mask, if exposure light is irradiated on this mask, a dark portion is formed at the shifter edge of the pattern end portion. As a result, part of a resist corresponding to the shifter edge is undesirably left without being exposed. Therefore, when a fine pattern or the like is to be formed using a Alternating phase-shifting mask, the mask must be elaborated to prevent generation of any unwanted residual resist.